Biomedical Engineering Reference
In-Depth Information
These fi stulae cause high rates of morbidity and mortality through the develop-
ment of sepsis, pneumonia, or bleeding from destruction of the carotid wall. The
permanent secretion from fi stulae and the cervical soft tissue defects (especially
of pharyngocutaneous fi stulae) is associated with a tremendous reduction of life
quality of patients and their stigmatization [24]. Due to postoperative salivary fi s-
tulae in oncological patients, their irradiation may not be possible within the
planned periods so that therapeutical aims cannot be reached. Contemporary
therapeutical options in the treatment of pharyngocutaneous fi stulae depend on
the size of fi stulae and on the indication of a postoperative adjuvant irradiation
therapy.
13.2.1
Applications of Different Implant Materials in Tracheal Surgery
In the 1950s, a great number of experiments for the tracheal reconstruction were
performed in animals using different materials like acrylresin [27], tantalum [28],
stainless steel [29], polyethylene [30], nylon [31],, and tefl on [32]. The great number
of materials used and the short survival time of the animals demonstrated that the
problem of tracheal reconstruction using implant materials could not be solved at
this time. The importance of biocompatibility of implant materials and the variable
requirements depending on the implantation site became obvious at the end of
the 1950s. After the successful application of Dacron
as arterial prosthesis
(1958), it was realized that an appropriate material was not available for the tra-
cheal reconstructive surgery showing the necessary elasticity, rigidity, and biocom-
patibility. At the end of the 1950s and the beginning of 1960s, there were fi rst
trials for the temporary application of polymeric implant materials in the tracheal
reconstruction. These materials were covered with mucosa from the urinary or
gall bladders to induce growth of connective tissues or bone around tracheal stents.
It was called temporary application because the implant material should be
removed after the newly grown cartilage or bone in the former tracheal defect zone
reached a suffi cient stability, so that the reconstructed tracheal tissues would not
collapse. Although cartilage and bone tissues could be demonstrated histologically
at the site of implantation, a suffi cient tracheal stability could not be gained in any
one of the animals and all animals died of respiratory insuffi ciency following
tracheal obstruction after the removal of the differently coated implant materials
[33, 34] . In the 1960s and 1970s, further materials were tested for tracheal recon-
struction, for example, Marlex
networks (polyethylene/polypropylene networks)
[35], silicon rubber [36], and Marlex
networks covered with cartilage and/or
tracheal mucosa [37, 38]. These new materials also did not fulfi ll the comprehen-
sive requirements for tracheal reconstruction regarding mechanical strength and
adequate fl exibility to avoid vascular corrosion induced by mechanical irritation.
These materials lacked biocompatibility, an air- and liquid tight integration of the
implant materials into the adjacent body tissues, an adequate stability against
bacterial invasion, and, especially, the epithelialization of the implants with a
functional tracheal epithelium [35 - 38] .
